I can't speak for the magickal part of it but being once a 3-dogs owner, have you try to spot what are the trigger moments when they behave aggressive towards each other? What age are these dogs and at what age did they start establishing their stance towards each other? My 3 dogs used to live under the same roof and while there are no major squabbles between them, I do keep a keen eye on the triggering factors.
Like humans, there can be so many factors contributing to a situation. Like one is beginning to establish itself as the alpha dog. Or perhaps another is resenting the lack of attention etc.